Apparatus for recombining hydrogen and oxygen and protectively returning water of recombination to the battery electrolyte

ABSTRACT

A HYDROGEN-OXYGEN RECOMBINING DEVICE FOR USE IN SECONDARY BATTERIES COMPRISES A CATALYTIC MASS AND AN ENCLOSURE BODY HAVE THE CATALYTIC MASS TOTALLY ENCLOSED THEREWITHIN. THE CATALYTIC MASS INCLUDES A REFRACTORY SUBSTRATE AND A PREDETERMINED QUANTITY OF CATALYTIC MATERIAL DISTRIBUTED ON THE SUBSTRATE. THE ENCLOSURE BODY CONSISTS SOLELY OF PLASTIC HYDROPHOBIC MATERIAL AND HAS A PORTION WHICH IS GAS PERMEABLE. THE HYDROPHOBIC MATERIAL, INCLUDING ITS PERMEABLE PORTION, PREVENTS LIQUID AND MIST FROM BATTERY ELECTROLYTE FROM ENTERING SAID BODY AND CONTAMINATING SAID CATALYTIC MASS. THE PERMEABLE PORTION PERMITS HYDROGEN AND OXYGEN TO ENTER SAID BODY AND CONTACT SAID CATALYTIC MASS. THE PERMEABLE PORTION ALSO PERMITS WATER VAPOR FORMED BY RECOMBINING THE HYDROGEN AND OXYGEN TO DIFFUSE FROM SAID BODY. THE CATALYTIC MASS HAS A CATALYTIC METAL CONTENT EQUIVALENT TO A PALLADIUM CONTENT OF NOT MORE THAN .1% BY WEIGHT OF THE SUBSTRATE. THE CATALYTIC MASS, WHEN INDUCING AN EXOTHERMIC REACTION TO RECOMBINE THE HYDROGEN AND OXYGEN, BEING CHARACTERIZED BY A LIMITED TEMPERATURE RISE WITHIN LIMITS BELOW THAT TEMPERATURE AT WHICH HYDROPHOBICITY AND PERMEABILITY OF THE ENCLOSURE BODY WOULD BE CHANGED.

June18,1974 E.L.KRE|DL ETAL 3,817,717

APPARATUS FOR RECOMBIHING HYDROGEN AND OXYGEN AND PROTECTIVELY RETURNINGWATER 0F RECOMBIHATION TO THE BATTERY ELECTROLY'IE Original Filed Harsh6, 1970 7 Sheets-Sheet 1 VOLTS AMPER ES June 18, 1974 KREmL ETAL3,317,717

APPARATUS FOR RECOMBIRI-NG HYDROGEN AND OXYGEN AND PROTECTIVELYRETURHING WATER OF RECOMBINATION TO THE BATTERY ELECTROLYTE OriginalFiled larch 6, 1970 7 Sheets-Sheet 2 June 18, 1974 E, KREI L ETAL3,817,717

APPARATUS FOR RECOMBINING HYDROGEI} AND OXYGEN AND PROTECTIVELYRETURNING WATER OF RECOMBINATION 1'0 THE BATTERY ELECTROLYTE OriginalFiled March 6, 1970 7 Sheets-Sheet '5 June 13, 19?4 KREIDL ETAL 3 837;?

APPARATUS FOR RECOMBIHING HYDROGEN AND OXYGEN AND PROTECTIVELY RETURNINGWATER 0F RECOMBINATION TO THE BATTERY ELECTROLYTE Original Filed March6, 1970 v 7 Sheets-Sheet 4 June 18, 1974 KRElDL ETAL 3,317,717

APPARATUS FOR RECOMBINING HYDROGEN AND OXYGEN AND PROTECTIVELY RETURNINGWATER OF RECOMBIHATION TO THE. BATTERY ELECTROLYTE Original Filed Batch6, 1970 7 Sheets-Sheet 5 fly. 6:

f 6"! l I 23.5" I I 7 /0 I fig 1a June 18, 1974 L v v APP nus FORRECOMBINI HYDROGEN A on AND P TECTIVELY nmuxmm mam OF REC BINA N To meBATTERY ELECTROLYTE KREIDL ET AL 3,81 7,717-

Original Filed March 6, 1970 v 7 Sheets-Sheath Gui-,-

June 13, 1974 KREIDL ETAL 3,817,711

APPARATUS FOR REGOMBINING HYDROGEN AND OXYGEN AND PROTECTIVELY RETURNINGWATER 0F RECOMBINATION 1'0 THE BATTERY ELECTROLYTE Original Filed larch6, 1970 '7 Sheets-Sheet 7 F5 2" 2 I 1 /.9 la I l I Ill llfk 20 R IUnited States Patent APPARATUS FOR RECOMBINTNG HYDROGEN AND OXYGEN ANDPROTECTIVELY RETURN- ING WATER OF RECOMBINATION TO THE BATTERYELECTROLYTE Ekkehard L. Kreidl, Wayland, Mass., and Richard G.

Acton, Prestbury, England, assignors to Koehler Manufacturing Company,Marlboro, Mass.

Original application Mar. 6, 1970, Ser. No. 17,070, now abandoned.Divided and this application Feb. 14, 1972, Ser. No. 226,041

Int. Cl. B01j 9/04; H01m 1/08, 35/00 US. Cl. 23-288 R Claims ABSTRACT OFTHE DISCLOSURE A hydrogen-oxygen recombining device for use in secondarybatteries comprising a catalytic mass and an enclosure body having thecatalytic mass totally enclosed therewithin. The catalytic mass includesa refractory substrate and a predetermined quantity of catalyticmaterial distributed on the substrate. The enclosure body consistssolely of plastic hydrophobic material and has a portion which is gaspermeable. The hydrophobic material, including its permeable portion,prevents liquid and mist from battery electrolyte from entering saidbody and contaminating said catalytic mass. The permeable portionpermits hydrogen and oxygen to enter said body and contact saidcatalytic mass. The permeable portion also permits water vapor formed byrecombining the hydrogen and oxygen to diffuse from said body. Thecatalytic mass has a catalytic metal content equivalent to a palladiumcontent of not more than .l% by weight of the substrate. The catalyticmass, when inducing an exothermic reaction to recombine the hydrogen andoxygen, being characterized by a limited temperature rise within limitsbelow that temperature at which hydrophobicity and permeability of theenclosure body would be changed.

This application is a divisional application of Ser. No. 17,070, filedMar. 6, 1970, and now abandoned.

This invention relates to improved methods and means for reacting gasessuch as hydrogen and oxygen in the presence of a catalytic device. Moreparticularly the invention is concerned with methods and means foroperating and periodically recharging a secondary battery systemthroughout a number of battery charging and discharging cycles Whilerecombining evolved hydrogen and oxygen gases in the presence of aspecial catalytic device which selectively receives the hydrogen andoxygen gases to form water vapor and which transfers the water vaporback to the battery electrolyte in a novel manner.

In recombining hydrogen and oxygen gases evolved during operation of asecondary battery by means of catalyst surfaces so that water vapor maybe formed and returned as liquid water to the electrolyte, variousdifficulties are encountered. This is especially the case when dealingwith a sealed secondary battery. For example, it is essential to dealwith the problem of resolving excessive gas pressures and maintainingthe catalytic device below temperatures which will result in ignitionand explosion of the gases. For a more detailed discussion ofdifiiculties, reference may be had to co-pending applications, Ser. No.866,531, now issued as Pat. No. 3,630,778, dated Dec. 28, 1971, and Ser.No. 866,633, now abandoned, both of Oct. 15, 1969, and in theseapplications there are disclosed improved techniques for controllingtemperatures at catalyst surfaces and regulating the rates at whichrecombination may proceed within safe limits.

A further difiiculty which develops in recombining gases with a catalystis the tendency for water vapor to condense and accumulate on thecatalytic surfaces in excessive amounts such as will flood the catalyst.If undesirable 3,817,717 Patented June 18, 1974 amounts of water doaccumulate, the excessively waterladen catalyst surfaces may becomede-activated and will thereafter fail to recombine the hydrogen andoxygen gases properly. This problem of water accumulation is complicatedby the fact that the catalyst surfaces must be protected from thechemical action of electrolyte spray such as sulfuric acid in leadbatteries or potassium hydroxide in nickel iron batteries, and thisinvolves using an enclosure body of some type. Where such an enclosurebody is used, it too may become excessively waterladen. In such asituation, the water vapor formed by recombination of gases may bereleased outwardly through the enclosure body very sluggishly andmovement of uncombined gases inwardly through the enclosure into contactwith the catalytic surfaces may be undesirably restricted. Thus after aperiod of time, either the gases may fail to reach the catalyst surfacesproperly or the catalyst surfaces may become de-activated.

It is, therefore, in general, an object of the invention to deal withthe problems indicated and to devise a catalytic enclosure techniquewhich is capable of transporting without interference and independentlyfrom each other (a) gases such as hydrogen and oxygen as they areevolved from a battery electrolyte during battery charging anddischarging operations, and (b) water vapor resulting from recombinationof stoichiometric quantities of gases such as hydrogen and oxygen in thepresence of a catalyst, while (0) substantially rejecting mist or sprayresulting from ebullition in a battery electrolyte as the hydrogen andoxygen gases are given off.

A further objective is to provide a selective gas transferral system bymeans of which gases such as hydrogen and oxygen may be continuouslymoved inwardly to catalyst surfaces while electrolyte mist or spray issubstantially excluded and yet water vapor resulting from recombinationof the gases within the transferral system may be expelled concurrentlywith inward travel of the gases. In other words, the passagesselectively distinguish between true vapors and fine electrolyte mist.

It is another specific object of the invention to provide an improvedmethod and means for operating a secondary battery, in particular asealed secondary battery, in which method water vapor resulting fromrecombination of hydrogen and oxygen in the presence of a protectivelycontained catalyst may be continuously removed and prevented fromaccumulating on the reactive surfaces of the catalyst.

Another object is to provide a combination of catalyst means and aselective gas transferral system in which water vapor resulting fromrecombination of hydrogen and oxygen gases may be expelled withoutsignificant change in the gas permeability characteristics of thesystem.

Still another object of the invention is to devise a catalytic devicewhich includes a catalyst and a special enclosure body formed withhydrophobic gas transferring means including gas inlets and water vaporoutlets for not only conducting gases inwardly, but also forcontinuously travelling water vapor outwardly from the catalyst to bereturned to the electrolyte as liquid water.

Still another object of the invention is to combine catalyst means witha selective transferral system which defines a small enclosure volumeinto which hydrogen and oxygen gases may be moved in response to partialgas pressure of these gases in a relatively larger surrounding volume.

And still another object is to devise a method of the class described inwhich exothermically induced rise in temperature within a catalyticdevice is controlled to prevent change in hydrophobic characteristics ofan enclosure body component of the catalytic device while returningwater of recombination to electrolyte.

With the foregoing objectives in mind and having regard especially forthe difficulties arising out of excessive water accumulation on catalystsurfaces and electrolyte attack, we have approached the problem from thestandpoint of seeking to provide a selective gas transferral techniqueby means of which hydrogen and oxygen gases may continuously come intocontact with catalytic surfaces concurrently with outward travel ofwater vapor resulting from recombination of the gases on catalystsurfaces, and with electrolyte spray or mist being excluded from cominginto contact with catalyst surfaces at all times.

A concept for a catalytic enclosure technique which distinguishesbetween gases, water vapor and electrolyte mist has evolved from a studyof certain conditions and characteristics inherent in a secondarybattery and its operation, and particularly a sealed secondary battery.Due to overvoltages, hydrogen and oxygen gas are usually evolved at thebattery electrodes, particularly during the charge cycle. The transportmechanism of hydrogen and oxygen from the electrodes, at which they areformed, to an enclosure for the catalysts is of importance to the aboveconcept. Initially the gases coalesce into bubbles in the electrolyteand when reaching its surface burst and generate electrolyte mist. Thegases released to the gas space above the electrolyte tend to dilfuse soas to equalize their partial pressure in the available space. However,in the presence of reactable gas mixtures of hydrogen and oxygen and ofan active catalyst combining them to form water, the ditfusionequilibrium is continuously disturbed by depletion of hydrogen andoxygen at the catalyst surface. This provides then a driving force forcontinued transport of reactable gases to the catalysts. This drivingforce in the following description is referred to as the partial gaspressure equalization force. Partial gas pressure is by definition thatpressure an individual gas would exert in a given volume if other gaseswere absent. If only one gas is present, partial and absolute gaspressures are identical. It also should be noted that water vapor formedat the catalyst surface within the enclosure will, by the samemechanism, tend to dilfuse towards the gas space to egualize its partialpressure over the entire gas space as determined by eventual return ofthe water to the electrolyte. This diffusion, however, is reinforced bythe thermal drive, discussed elsewhere.

Secondly, the battery electrolyte from which gases are evolved isusually a relatively concentrated aqueous solution of an acid or analkali and thus tends to be repelled by hydrophobic substances. Thirdly,the reaction of hydrogen and oxygen in the presence of a catalyst is anexothermic reaction producing water vapor and appreciable heat.Fourthly, water vapor resulting from evolving hydrogen and oxygen mustnot be condensed within the enclosure body but rather on the electrolytesurface or any of the surfaces occurring externally of the enclosurebody.

With these conditions in mind, we have devised an improved method of gasrecombination and return of water of recombination to an electrolytebased on a novel selective gas transferral technique. This selective gastransferral technique proceeds from our having determined that certainhydrophobic materials which can repel aqueous electrolyte materials may,at the same time, serve as a medium for transmitting gases and watervapor. In addition, the .transferral technique makes use of the partialgas pressures generated in a battery during opera tion, and furtherutilizes the heat resulting from the exothermic reaction when watervapor is formed to transport the water vapor out of the enclosure body.

In carrying out our improved method of gas recombination, we provide acatalytic device which preferably includes a bed of catalyst surfacescontained in a specially designed enclosure body. An essential featureof this enclosure body is that it includes a specific form ofhydrophobic material which is characterized by being resistant toelectrolyte mist or spray and by an especially controlled permeabilityto thereby constitute a gas transfer means which provides gas inlets andpreferably also water vapor outlets. The gas inlets are comprised bysmall openings or preferably pores which, while being capable ofsubstantially excluding electrolyte mist or spray, are neverthelesspermeable by hydrogen and oxygen in response to partial gas pressureequalization forces generated in the volume of a battery surrounding thecatalytic device.

The size of the enclosure body containing the catalyst will bedetermined by the amount and shape of individual catalysts used. So asto take full advantage of the thermal drive, as described below, forremoval of Water vapor the catalyst should be uniformly distributedwithin the enclosure body so that the exothermic reaction of waterformation heats the enclosure uniformly and does not lead to cold spotswhich could cause water vapor condensation. Wherever possible, the spacewithin the enclosure body should be filled with not substantially lesscatalysts than can be achieved by loosely packing them into theavailable space. This packing factor should not leave more than an emptyvolume of about 30% above the highest point reached by any catalyst inthe enclosure body when loosely packed in the enclosure body.Preferably, however, the enclosure body should be so designed that nosubstantial free volume remains above an at least loosely packedcatalyst bed. Alternatively, the catalysts can be packed less densely ifthey are reasonably evenly distributed within a hydrophobic spacermaterial, such as used in commercially available recombination devices.The spacer materials may be hydrophobic powder or fibers or waterproofed powders or fibers of any suitable kind. We have determined thatby reacting hydrogen and oxygen gas on catalyst surfaces within anenclosure body of relatively small volume, it becomes possible to set upa controlled thermal gradient in which temperatures in a relativelysmall volume within the enclosure body resulting from the exothermicreaction between hydrogen and oxygen are constantly at levels higherthan temperatures in the battery space occurring outside the enclosurebody.

There may thus be realized a thermal drive" which functions to preventcondensation of water vapor within the enclosure body so that the watervapor seeks to pass through gas outlets of a capillary size in theenclosure body to condense at surfaces which are at the lower end of thetemperature gradient. Water outside of the enclosure body, whether aswater vapor or water condensed on the surfaces forming the space abovethe electrolyte and around the enclosure body is returned to theelectrolyte by virtue of the desiccant nature of the electrolyte orlowering of the water vapor pressure above it or in the case ofcondensed water also by gravity when the battery is in an uprightposition.

The nature of the invention and its other objects and novel featureswill be more fully understood and appreciated from the followingdescription of preferred embodiments of the invention selected forpurposes of illustration and shown in the accompanying drawings, inwhich:

FIG. 1 is a diagrammatic view illustrating a battery system which may beoperated and periodically recharged in accordance with the recombinationmethod of the invention;

FIG. 2 is a plan view of a battery of the general type indicated in FIG.1;

FIG. 3 is a side elevational view of the battery with portions brokenaway to illustrate a catalyst recombining means in the battery;

FIG. 4 is a vertical cross-sectional view of the battery shown in FIGS.2 and 3;

FIG. 5 is an elevational view illustrating fragmentarily a batterycharging apparatus with which a battery may be recharged;

FIGS. 6, 7 and 8 are detail views illustrating diagrammatically one formof catalytic device used in the battery shown in FIGS. 1-5;

FIGS. 9-17 illustrate three other forms of catalytic devices of theinvention.

Our improved method, in general, therefore, includes evolving andconfining hydrogen and oxygen gases in a closed gas space of a secondarybattery in the presence of a catalytic device in which catalyst surfacesare protectively contained in an enclosure body and maintained in asuitably reactive state for desired operating periods. The closed gasspace for confining the evolved gases and the catalytic device refers tothe gas space commonly provided above the electrolyte in secondarybatteries which is vented to the outside. In a sealed battery this gasspace is hermetically sealed, even though a release valve may beprovided to allow venting above predetermined pressure levels. Theenclosure body is made with gas inlets comprised by a hydrophobicmaterial which positively repels aqueous electrolyte mist or spray. Thehydrophobic material present in the enclosure body is characterized by aselective gas permeability such that when the enclosure body issupported in the closed gas space of the battery, hydrogen and oxygengases evolved therein may, in response to partial gas pressuresdeveloping, be continuously moved inwardly through the enclosure bodyinto contact with the catalyst surfaces.

The hydrophobic portions of the enclosure body are also made with a porestructure which permits water vapor to travel outwardly. The volume ofthe enclosure body is made as small as possible so that the heat ofexothermic reaction resulting from recombination of hydrogen and oxygengases on the catalyst surfaces within the enclosure body sets up athermal gradient within safe operating temperatures and produces asubstantial thermal drive capable of causing water vapor to becontinuous ly travelled outwardly through the enclosure. We have found,for example, that temperatures of and even as low as 1 above ambienttemperature in a battery space is sufficient to provide this thermaldrive.

Temperatures generated at the catalyst surfaces as a result ofexothermic heating are continuously controlled in accordance with thetemperature resistance of the hydrophobic catalyst enclosure body inorder to prevent change in the hydrophobicity and permeability of thematerial from which the enclosure body is formed.

We have determined that the desired selective characteristics can berealized by proper combination of hydrophobicity, gas permeability, sizedistribution, and structure of the inlets or pores for exclusion ofmist. These properties, for example, can be designed into hydrophobicmaterials, such as the preferred fluorinated hydrocarbon polymers asbased on tetrafluoroethylene, fiuoroethylenes or fluorinated propylenecopolymers, during fabrication steps, such as by proper sintering ofpowders or fibers or by perforating intrinsically non-porous shapes. Thema terials may be fabricated into-rigid bodies of any shape, such astubular bodies, or in the form of flexible shapes such as membranes andtapes. For non-porous portions of enclosure bodies, where such aredesired, non-porous materials of such hydrophobic materials can befabricated as well in the form of rigid bodies or flexible sheets ortapes. Usually, however, such non-porous portions will be used as rigidsupporting structures unless they are used as protective liners, etc.,for materials which are not intrinsically hydrophobic.

As noted above, we have found that we may control selective gas transferby regulating permeability as Well as hydrophobic nature in a catalystenclosure body, and as one specific instance, there may be cited acatalytic device of satisfactory nature in which catalyst means isenclosed by a thin membrane of a fluorinated hydrocarbon polymer such astape made from Teflon. Teflon is a registered trademark by the E. I. duPont de Nemours Company for such materials and is manufactured and soldby it. In this connection, we found the tape may have 6 a thickness ofapproximately .001 to .003 inches and may have a controlled permeabilitycharacteristic which is capable of transferring stoichiometric hydrogenand oxygen gas mixtures equivalent to the gas generated by electrolytewater at about 5-30 amps per square centimeter of exposed tape surface.

It will be understood that the above example is not to be taken aslimiting the invention thereto. For example, we have also used suchfluorocarbon-based, porous, hydrophobic materials such as Teflon as aremade for filter purposes having a regulated permeability characteristicequivalent to about 50 to 70 amps per square centimeter and inthicknesses up to .050 inches. Preferred results form the standpoint ofelectrolyte protection as a matter of fact may be realized with thesemembranes occurring in the higher range of thicknesses noted.

In addition to the fluorinated hydrocarbon polymers indicated, certainother hydrophobic materials having suitably regulated permeabilitycharacteristics may be comprised by compounds such as silicone polymers,fluorinated vinyl chlorides, polypropylene, high temperature nylon, andothers. It is also possible we find to use nonhydrophobic andnon-electrolyte resistant materials and coat them with hydrophobicsubstances to combine suitable permeability with satisfactoryelectrolyte resisting characteristics. Thus such materials can be usedif coated with a hydrophobic material such as a fluorinated hydrocarbonpolymer dispensed from pressure dispensers. We may thus convertrelatively inexpensive hydrophilic porous bodies or membranes into asatisfactory catalytic enclosure body with an external hydrophobicsurface.

As one specific example, there may be cited the use of porous highsilica glass tubes where such materials are used for water vaportransfer which are rendered hydrophobic by coatings on one or bothsurfaces. We also find that certain other plastics are sufficientlyhydrophobic for rejecting electrolyte mist, but their use is limitedbecause of their lesser chemical and temperature resistance. Use ofthese compounds is limited as they become increasing wettable whenattacked by strong acids or alkalis.

While the term hydrophobic is generally well understood, it might bestated that a substance is considered hydrophobic if its surface tensionis significantly less than that of water or 32 dynes/ cm. A more usefuldefinition for those skilled in the art, particularly in determiningwhether a substance is hydrophobic with respect to any givenelectrolyte, is the contact angle of a drop of electrolyte placed on thesurface of a material to be evaluated for hydrophobicity. If the droptends to spread, i.e. the contact angle is greater than the material canbe considered as wetting or hydrophilic. Conversely, if the contactangle is less than 90 the material evaluated is hydrophobic with respect to the electrolyte. Particularly important is the fact thatmaterials which are not resistant to the chemical and/ or temperatureenvironment in a battery recombination device may change theirproperties with time and this is why fluorinated hydrocarbon polymers,because of their known history of temperature and chemical resistance,are generally preferred.

It will be understood that an essential feature of the catalytic deviceof the invention using any of the materials noted above is that all gasinlets, that is, openings whether macropores or holes or micropores, besubstantially comprised by hydrophobic materials at least on the outsideof the enclosure body, that is where the catalytic device faces the gasspace or spaces from which it receives the reactable gases, i.e.,hydrogen and oxygen, by partial pressure equalization forces, whetheraided by diffusion or convection. Dependent on the specific use andparticularly on the severity of expected electrolyte spray, otherportions of the enclosure body may be different in nature.

In addition, water vapor removal may be etfected in part throughmaterials which are hydrophilic in nature and have a hydrophilicoutside. Eflecting at least partial water vapor transfer by means ofsuch hydrophilic materials may be of advantage in situations where thereis only a small thermal drive such as at or after the end of gassing oncharge when only small residual amounts of water vapor are generated bythe catalysts. The hydrophilic portions in the enclosure body then willpreferentially absorb the water vapor from where it will be eitherslowly transferred due to concentration equalization with theelectrolyte by vapor transfer and/or will be stored until thermallydriven off at subsequent more active recombination cycles.

Such hydrophilic materials may or may not be gas permeable, at any rate,their gas permeability tends to decrease the more water they absorb, andparticularly when wetted by electrolyte spray even highly and relativelylarge pored porous hydrophilic materials may become completely gasimpermeable. However, if such hydrophilic materials have sufficientporosity and a suitable pore structure to both allow gas flow in andwater vapor flow out, they can be used as a total body enclosureprovided the outside thereof is enveloped by a hydrophobic materialsubstantially excluding electrolyte spray and they are sufiiciently gaspermeable to provide sufiicient gas inlets and water vapor outlets.

It is pointed out that the invention may be practised with variousmodifications as determined by specific design needs and by followingthe selective gas transferral technique herein described. Thus gasinlets and vapor outlets may be provided by holes in a hydrophobicenclosure body structure (which is quite satisfactory in usescharacterized by little electrolyte spray or in batteries which aretrickle charged as a rule), or the entire structure may be porous,preferably microporous in nature for complete exclusion of spray evenunder severe conditions (such as in batteries which need to be rapidlyand/0r deep charged). Alternatively, a hydrophilic portion, primarilyfor outwards water vapor transfer, may have hydrophobic caps with gasinlets. Hydrophilic portions may be protected with hydrophobic gaspermeable material on the outside and/or inside, etc. Finally, if thebody enclosure contains extensive gas impermeable portions on theinside, these portions must be of hydrophobic material to minimizenucleation of water vapor to form liquid water.

We have further found, and this forms part of our invention, that forbattery uses which may encounter situations unfavorable to producing areliable thermal drive, it may be advantageous to supply low level heatto the interior of the enclosure body. As noted above temperatures ofand even as low as 1 above ambient sutficient to provide this thermaldrive and a range of up to 50 above ambient is acceptable. Thegeneration of such temperatures needs only low power inputs and may beaccomplished by means such as, for example, electrical heating means andis not associated with hazards which can be encountered with heatersused to evaporate water once it is condensed.

In carrying out our improved method of recombining gases such ashydrogen and oxygen utilizing a catalytic device of the form notedabove, we may desire to utilize the catalytic device with any type ofbattery or battery operation wherein recombination of gases is desired.However, without limitation, there is noted below illustrativeconditions present in a typical miners lamp battery or in a modifiedsealed version thereof, which is subject to extended charging operationsin the course of which appreciable amounts of gases are produced.

For example, one very common miners lamp battery has a nominal rating of4 volts resulting from two cells in series. It has an ampere-hour ratingof 12 at a hour discharge rate, one tubular type positive plate and twopasted negative plates per cell, and electrolyte-absorbing separatorswhich, with the plates, contain all but about ml. of the 170 ml. ofelectrolyte in each cell.

A gas space of approximately 75 ml. is provided above the plates in eachcell and temperatures may range from 10 C. to 38 C. Such a batterytypically is discharged daily for 10 hours through a lamp with rating of1.0 ampere at 4.0 volts and is charged for 14 hours daily by means of acharger with output of 4.4 volts and 1.2 amperes at the beginning ofcharge and 5.1 volts and .90 amperes at the end of charge. For example,one very common miners lamp battery has a nominal rating of 4 voltsresulting from two cells in series. It has a 12 ampere hour rating at a10 hour discharge rate, one tubular type positive plate and two pastednegative plates per cell, and electrolyte-absorbing separators which,with the plates, contain all but about 20 ml. of the 210 ml. ofelectrolyte in each cell.

Such a battery typically is discharged daily for .10 hours through alamp with a rating of 1.0 ampere at 4.0 volts and is charged for 14hours daily by means of a charger with output of 4.4 volts and 1.2amperes at the beginning of charge and 5.1 volts and .90 amperes at theend of charge. Normal ambient temperature during discharge isapproximately 15 C. and during charge is in a range between 10 C. and 30C. In this typical operation, hydrogen and oxygen may he evolved intotal amounts which are quite variable from cycle to cycle but whichaverage at standard pressure and temperature approximately 700 ml. percell per charging period and about 5% as much, or 35 ml., during thedischarge period. When the typical miners lamp battery is sealed with anefficient recombination device, gas pressure fluctuations many rangebetween atmospheric (starting condition) and forty p.s.i.g. (averagesetting of release valve). On the average the amount of water returnedis about onethird at milliliter per cycle. Of course, this does notoccur within every cycle but may fluctuate from practically no waterreturn in some cycles, with compensating higher returns in others. Lossof water by operation of the release valve due to excessivenon-stoichiometric gassing in a few cycles was negligible in most casesand usually less than a few milliliters for a projected 300 cycle life.Recombination was as a rule effected by an excess amount of catalystssuch as 5-10 gms. of catalysts having .01 to .5 palladium on porousalumina substrates having surface areas from about one sq. m./ g. to sq.m./g. and intrinsically being capable of combining 10-20 ml. per minuteof stoichiometric hydrogen-oxygen mixtures.

FIG. 1 illustrates one form of selective gas transferral system of theinvention including a miners lamp battery of the class above-described,a typical miners lamp and a battery charging apparatus. As showntherein, numeral 206 denotes the miners lamp together with a sealedsecondary miners lamp battery 202 of the lead-acid type with which themethod and means of combining hydrogen and oxygen gas as hereindisclosed may be employed. One form of catalytic device of the inventionis illustrated diagrammatically within the battery 202 and is indicatedby arrow E. Numeral 204 refers to a conventional battery chargingapparatus, having a battery charging rack, of the class commonlyutilized by miners in placing a battery on charge at the end of theworking day. The battery 202 is illustrated in further detail in FIGS.24, inclusive, and details of the charger 204 and charging rack 201 areshown in FIG. 5.

It will be understood that the battery 202 is placed in use by a mineras he uses his miners lamp and discharge takes place. At the end of aworking day the miner places the lamp on charge in the charging rack 201as shown in FIG. 5. This cycle is repeated over a desired working lifeof the battery. Hydrogen and oxygen gas evolved during these batteryoperations collect in the closed spaces A and B of the battery and moveinto contact with the catalyst device E under varying pressures asearlier described.

In the apparatus indicated in FIG. 1, means are pro vided forillustrating the battery on discharge and for charging from a batterydischarge operation to a battery charging operation in one simple way.For example, in placing the battery 202 on discharge, a circuit from thepositive side of the battery 202 is completed through a lamp 206 andback to the negative side of the battery by moving the double throwswitch poles 208 and 210 into contact with switch contacts 212a and214a, respectively. Current is then generated in the battery in theusual manner and energizes the lamp 206. Such a battery dischargeoperation is intended to be representative of daily use of the batteryby a miner.

When the battery is to be recharged the battery is connected to charger204. Switch poles 208 and 210 are then moved into contact with batterycharging switch contacts 212 and 214. This disconnects the lamp 206 andcompletes a circuit from the charger 204 through the battery 202 andcharging then takes place. Such a battery charging operation is intendedto be representative of a miner placing battery 202 in a charging rack201 as suggested in FIG. 5. The battery during its charging operationevolves gases which are confined in the sealed battery 202 in one ormore closed spaces and exert fluctuating pressures. Pressures thusexerted may act through a transducer 218 and when desired may providesignals for actuating an electrical recording system 220 as indicated atthe lower right-hand side of FIG. 1, where arrangements for monitoringvoltage and ampere during charge and discharge are also indicated.

Further details of battery 202 are shown in FIGS. 2-4 and as indicatedtherein, the battery is made with a body portion having suitablestrength characteristics and further provided with a sealed top 202a. Inthis body portion is a battetry partition 230 which divides the batteryinto two cells.

Assuming that the battery 202 is illustrative of the 4-volt miner'sbattery earlier described, the battery casing or body portion isconstructed of a material having a strength which will withstand apredetermined range of pressures exterted in the 75 ml. gas space ofeach cell of the battery. For example, we may employ a polycarbonateplastic to provide the necessary strength. Polycarbonate plastics may bedescribed as polymeric combinations of bi-functional phenols orbisphenols, linked together with a carbonate linkage.

In utilizing a plastic material such as polycarbonate we have, forexample, determined that the miners lamp battery 202 may be constructedto contain a range of pressures extending from pressure all the way upto as high as 75-80 p.s.i.g. or higher. In addition, the overall size ofthe battery is regulated in accordance with the specific plateconstruction and quantity of electrolyte employed.

Contained in the cells referred to are positive plates 232, separatormembers 234, negative plates 236, electrolyte 238 and insulator means240. The electrolyte is employed in an amount such as 210 mls. toprovide a liquid level which covers the tops of the plates. Immediatelyabove the electrolyte are spaces A and B providing the specified volumeof 150 mls. in each cell in which gases evolved in the operation of thebattery may be sealably contained. Conventional electrical conductorcables and terminals are provided as shown in FIG. 3. Ambienttemperatures in the spaces A and B may range from C. to 30 C or higherduring the charging period and may be about C. during the usualdischarge period.

While it is contemplated that for certain battery systems it may bedesirable to provide a completely sealed gas space, it is preferable toemploy a pressure relief valve which may be regulated in accordance witha predictable range of pressure fluctuations to provide for confininggas within predetermined releasable limits. The limits referred to areintended to fall below the maximum pressure-retaining capabilities ofthe battery and may, for example, be of from 30 p.s.i.g. to 70 p.s.i.g.A relief valve V, suitable for this purpose, may be mounted in thebattery top in a position to communicate with the gas space as shown inFIG. 3.

In carrying out our method, we recombine gases in Y battery 202 by meansof the catalytic device E which may be supported in the battery aboveelectrolyte 238 on the partition wall 230 as shown in more detail inFIGS. 2-4 inclusive. The catalytic device also includes, as a principalcomponent, a hydrophobic enclosure body 235 which is shown in moredetail in FIGS. 6-8 inclusive.

As shown in FIGS. 24 inclusive, on top of partition wall 230 there islocated a perforated tray 231 formed with perforations 233. Thecylindrical enclosure body 235 is shown resting on a fiber glass mat237. Since the enclosure body is cylindrical in shape, it will be seenthat it has only a small area in contact with fiber glass mat 237 andreactable gases thus have free access to the circular sides of theenclosure body 235. Any water condensed near enclosure body 235 candrain through fiber glass mat 237 while on the other hand, this matprotects the enclosure body 235 from direct contact with electrolytespray emanating from electrolyte 238 directly beneath it.

In accordance with the invention, we provided in the catalytic device E,a hydrophobic enclosure body 235 which includes a cylindrical memberclosed at either end by circular walls or caps C1 and C2. Thecylindrical member as illustrated in FIGS. 6 to 8 inclusive, is formedof a relatively thick non-porous layer of a hydrophobic material such asTeflon of the type earlier described, while the caps C1 and C2 areformed of relatively thin portions of the Teflon membrane.

The caps C1 and C2 are designed to have a degree of gas permeabilitywhich will, in response to partial gas pressures in the battery, providefor hydrogen and oxygen gases evolved in the battery spaces A and B(FIG. 2) moving into the space within the cylindrical member.

Furthermore in accordance with the invention, we provide within theenclosure member a plurality of catalyst pellets, P1, P2, P3, etc. ofcontrolled recombination capability. The pellets are preferably arrangedin a bed or mass, being loosely piled upon one another as shown in FIGS.6-8. Each of the pellets P1, P2, P3, etc. includes a substrate materialsuch as alumina in which a catalyst metal such as palladium isimpregnated or coated. The recombination capability of each of thepellets is regulated in accordance with the quantity of gases evolved inbattery 202 which are required to be recombined, and also in accordancewith the temperature resistance of the hydrophobic material Teflon ofwhich the enclosure body 235 is formed.

As an example of catalyst specifications suitable for controllingcatalyst temperatures and safely recombining gases evolved in the closedgas space of the miners lamp battery 202, there may be employed forenclosure body 235 a cylindrically shaped member having a length of 1inch and inches defining an enclosure space 'of about .75 cubic inches.In this space, there may be contained 10 grams of the catalyst pelletsP1, P2, P3, etc. The enclosure body, having a volume of only 2 to 3cubic centimeters, thus comprises a relatively small volume in relationto the millimeter volume comprised by the enclosed battery spaces A andB.

Each of the catalyst pellets P1, P2, P3, etc. were formed from aforaminous substrate of alumina in which was provided a predeterminedquantity of palladium impregnated or coated on each pellet to provide aconcentration of, for example, .1% per weight of palladium on an aluminasubstrate having internal surface area of about .3 sq. m./g.

As noted above in a typical daily use of the battery 202, hydrogen andoxygen may be evolved at a rate of 700 ml. and may exert a combinedpressure in the battery spaces A and B of from 0 p.s.i.g. to 40 p.s.i.g.In accordance with the invention, the hydrogen and oxygen gases thusevolved in the spaces A and B of battery 202 in response to partial gaspressure equalization forces, moved inwardly through the hydrophobicportions of the caps C1 and C2 into contact with the surfaces of thepellets P1, P2, P3,

etc. These catalyst surfaces recombined hydrogen and oxygen gases as acontinuous exothermic reaction in the enclosure body 235 to form watervapor. The temperature induced by the exothermic reaction was found toproduce a rise'in temperature within member 235 of, for example, 40 C.and this rise in temperature provided a positive thermal gradientbetween temperatures 'within the enclosure body 235 and temperatures inthe spaces A and B outside this enclosure body occurring at ambienttemperatures. As earlier noted a typical thermal gradient may becomprised by a temperature of 40 C. and a temperature of 18 C. in thespaces A and B. The rate at which recombination proceeded was controlledper unit surface of the catalyst in accordance with the invention byregulating the gas recombination capability of the catalyst surfaces asnoted above so that temperature resulting from exothermic heating couldnot exceed upper limits at which the enclosure body 235 could be usedwithout change in permeability or hydrophobic character, andspecifically the gas recombining capability was so limited that evenunder the most adverse conditions rise in temperature could be heldwithin a range of from 200 C. to 250 C.

Water vapor resulting from recombination of the gases by reason of thecontrolled thermal gradient described was prevented from condensing onthe inside of the member 235, and in response to the thermaldrivedescribed moved through the caps C1 and C2 which provided, due totheir porous structure, both water vapor outlets as well as gas inlets.Water vapor transferred through the caps C1 and C2 was returned theretodirectly or indirectly as described above. The performance of a battery202 illustrated in the figure was in the range described for a sealedmodification of a miners battery described above.

At the end of the operating period noted, it was found that no wateraccumulated within the enclosure body and the quantity of electrolyteremained substantially unchanged, thus clearly establishing the factthat positive return of water vapor from the enclosure body to theelectrolyte was continuously carried out in an improved and safe manner.

From the above description of a typical miners lamp battery inoperation, it will be seen that the selective gas transferral method ofthe invention involves moving gases into a gas permeable hydrophobicenclosure body which repels electrolyte material and which in responseto an induced thermal drive constantly returns water vapor to anelectrolyte body. Concurrently, the temperature of catalyst surfaces inthe enclosure body are controlled in accordance with the temperatureresistance of the enclosure body so that a limited degree of exothermicheating may be utilized to return the water vapor to the electrolytewhile preserving the hydrophobicity and permeability of the enclosurebody substantially unchanged.

As noted in the miners lamp battery above described, one desirable wayof controlling catalyst temperatures, we find, may be realized bylimiting the intrinsic gas recombining capability of the catalystsurfaces within both upper and lower limits which are consistent withbattery gassing conditions and which prevent a temperature rise tovalues at which the hydrophobic enclosure body starts to lose itshydrophobicity and/or gas permeability.

In this connection, we have determined that we may also desirablycontrol exothermic heating in our catalytic device in several other waysto preserve the efiiciency of It will be observed that by reason of thefact that our selective gas transferral technique is based upon the useof a gas permeable enclosure body, we are enabled to prevent suddenonrush of gases and to keep a flow of gases moving into contact with thecatalyst surfaces at a relatively uniform rate and within predeterminedlimits which are capable of being adjusted to a necessary, but known,intrinsic gas recombining capability of catalyst surfaces employed.

It is a further desirable feature of our gas transferral technique thatwe may control the permeability of the enclosure body 235 in relation tothe contained catalytic surfaces of the pellets P1, P2, P3 so that theyco-act or -cooperate with one another to maintain a predetermined rateof recombination which will keep temperatures at the catalyst surfaceswithin acceptable limits, and particularly below temperatures at whichthe enclosure body may be physically or chemically changed, i.e. above250 C. for any substantial length of operating time.

It is pointed out that the disclosed composition of the enclosure body235, and the specific palladium pellets P1, P2, P3, etc., noted areintended to be illustrative of controlling permeability of the enclosurebody in relation to the intrinsic recombination capacity of thecatalytic surfaces contained therein so as to provide for recombinationof gases with exothermic heating being held within safe operatingtemperatures, and specifically, below temperatures of 250 C. and higher.

Regulating exothermic heating by controlling intrinsic recombiningcapability of a catalyst may be carried out in various other ways asdisclosed, for example, in considerable detail in application Ser. No.866,633, Improvements in Construction and Operation of RechargeableBattery Systems of Chemically Generating and Electrical Currents andSer. No. 866,531, Methods and Means of Recombining Hydrogen and Oxygenin a Sealed Battery and Controlling Recombination at Catalyst Surfaces,and it is intended that any of the various forms of catalysts describedin application Ser. No. 866,633 and Ser. No. 866,531 as well as themethods of preparing such catalysts may be employed in carrying out themethod of the present invention.

Thus control of temperature by limiting intrinsic recombinationcapability of a catalyst may be more fully understood from aconsideration of a number of factors to be taken into account and whichare reviewed in application Ser. No. 866,633.

As noted therein, it has been recognized that recombination of hydrogenand oxygen by means of a catalyst is an exothermic reaction whichaccelerates with the rate of gassing and/or partial pressures ofstoichiometric hydrogen and oxygen to raise the temperature of thecatalyst. It has also been assumed that oxygen and hydrogen are firstabsorbed at the catalyst surface where they react to form water in thecondensed form which then evaporates. An example of a catalytic site isamorphous palladium metal on a catalyst support such as porous alumina.Dependent on the heat dissipation properties of the catalyst and of thesurrounding enclosure body, the temperature and nature of theenvironment, including importantly the pressure, etc., the heatgenerated by the exothermic reaction may thus more or less raise thetemperature of the catalytic surface to thereby raise its activity andgenerate more heat. If there is anample and rapid supply of oxygen andhydrogen, this can cause a runaway process which will lead to athermally or free radical initiated ignition in the gas space withtemperatures rapidly increasing to above 600 C. where combustion orexplosion can take place.

As set forth in application Ser. No. 866,633, it has been determinedthat a recombination device can provide complete recombination ofhydrogen and oxygen in a battery at a satisfactorily rapid rate butWithin predetermined limits of temperature by controlling the reactionrate per unit of area of catalyst exposed to a free gas space in such amanner that within the design parameters of such a battery with respectto gas composition, pressure and ambient temperatures, the temperatureas measured at catalyst surfaces will not reach a value at whichcombustion or explosion preceeds into the gas space under the mostadverse conditions, and may, in fact, be held substantially lower withinupper limits of from 400 C. to 600 C. and preferably below 250 C. orless.

In application Ser. No. 866,633, it is disclosed that this may be doneby adjusting the palladium content of a catalyst and surface area of thecatalyst in convective and/ or radiant and conductive contact with asurrounding battery structure and catalyst surfaces were observed to bereduced in temperature from 600 C. down to approximately 250 C., and asillustrative of this control application Ser. No. 866,633 disclosed acatalyst device in the form of a small cylindrical foraminous pellethaving diameter of 1.6 mm. and an axial length of 3.8 mm. and havinginternal surface area of about 90 square meters per gram, and apalladium content of about .54% by weight. This catalyst reached atemperature of 600 C. when subjected to a gassing rate of 2 to 3 amps,i.e. about 1.35 to 1.50 liters of stoichiometric gas. The same testprocedure was carried out with the catalyst device changed to provide alower palladium content. The cylindrical foraminous pellet was made witha diameter of $5 of an inch and a length of 95 of an inch and thepalladium content was .01% by weight on a surface area less than 1square meter per gram. This device when exposed to gases showedtemperatures reduced to 200 C. and lower.

In application Ser. No. 866,531 there has been disclosed a compositecatalytic device which we may desire to employ in our present inventionand .attention is again directed to details of the disclosure in Ser.No. 866,531 for a discussion of specific forms and use of thesecomposite catalysts. As disclosed in Ser. No. 866,531 the compositecatalysts are comprised by a nucleus of catalytic material of relativelyhigh level gas recombination capability which can control recombinationof gases in a very positive manner and provide cumulative heating for anouter surrounding body of catalytic material of lowlevel activity.

In practice such composite catalysts are most easily realized by eitherone of two approaches. In the first approach a bed of catalysts havingless than .1% palladium by weight, preferably on a porous aluminasubstrate having not more than 1 sq. m./g. surface area, will provide athermally favorable condition in the nucleus or center of the bed, thuspermitting easy start up. Due to the low level impregnation and lowsurface area such a bed prevents over heating. In the second approach anindividual composite catalyst may be prepared by having a highly activecatalyst (such as more than .2% palladium by weight on porous aluminahaving more than 10 sq. m./ g. surface area) may be enclosed by a lowactivity shell of the properties described for the bed above. Palladiumimpregnated alumina substrates are generally preferred foroxygen-hydrogen recombination. However, if desired, equivalent catalystmaterials using e.g. other noble metals, such as platinum, rhodium, oriridium and other substrates, such as other refractories like magnesia,zirconia, charcoal, graphite, silicon carbide, etc. may be employed.

It has also been disclosed in application Ser. No. 886,- 531 that whenutilizing a composite catalytic, a self-limiting temperature effect maybe realized in a battery when hydrogen and oxygen pressures increase. Atsuch time, there is caused to take place heat release from outercatalytic surface of the composite catalyst and in increasing degree bymeans such as radiation, conduction and convection until the heatrelease equals or exceeds exothermically induced heat in the exposedcatalyst surfaces and then temperature ceases to rise.

While temperature control by catalysts of this kind and by other meanshave been described in these copending applications, which are includedherein by reference, it is important to understand that one modificationof our invention as disclosed herein is based on our discovery that theuse of such controlled catalysts in combination with enclosure bodieshaving hydrophobic portions providing gas inlets as well as at leastpartial gas outlets leads to superior catalytic devices and tounexpected results. The combination of such catalysts with suchenclosure bodies provides, for example, (a) superior start-up for lowlevel catalysts beyond that achieved in these copending applications dueto the virtual elimination of mist without (b) endangering theproperties of the hydrophobic enclosure body due to the temperaturecontrolled catalysts and (c) enhancement of the thermal environment forthe start-up in the nucleus which in turn enhances vapor transferthrough a hydrophobic material, thus minimizing water condensation onthe catalysts proper.

In accordance with our present invention the hydrophobic gas inlets ofthe enclosure body can be utilized to provide for flow limitations ofthe reactable gases and thus we can in another way control thetemperature of the catalysts. Thus the single small openings havingabout a 3 mm. ID and 8 mm. length in the Examples 1 through 4 or themembranes as used in Examples 5 and 6 and as described previously inthis specification provide sufficient flow restriction to provide thedesired tempera ture control. However, we prefer for overall safetyreasons, to use catalysts which are intrinsically temperature limited asdescribed above.

It is intended that catalytic devices such as these may be employed inthe present invention in either the form shown in the device in FIGS.1-8 or in various other devices such as those illustrated in FIGS. 9-20,inclusive.

In addition to the form of catalytic device shown in FIGS. 1-8 we mayalso desire to employ various other modified forms of catalytic devices.Thus in FIGS. 9-11, inclusive, there is illustrated another form ofcatalytic device of the invention in which a bed of pellets P6 iscontained within a tubular enclosure body P1, formed with perforationsG. This tubular enclosure body is closed at opposite ends by perforatedend portions C3 and C4. The perforated enclosure F1 together with endportions C 3.and C4 are comprised by a hydrophobic material Of the classreferred to above, and consisting of Teflon, for example, these partsare preferably constructed of a thickness suitable to support aretaining structure for the pellets and located around these parts is acontinuous relatively thin membrane M of hydrophobic material such asTeflon.

This arrangement is preferred where it is desirable to have the entireenclosure body surrounded by a membrane with the perforated portions F1,C3 and C4 serving as support for the membrane. Evidently thisarrangement allows access of gases as well as removal of water vaporfrom all sides and will be particularly suitable for enclosure bodies ofan elongated cross-section to facilitate access to gases and removal ofwater vapor.

In FIGS. 12 to 14, inclusive, another form of catalytic device isillustrated which includes a bed of catalytic pellets P7 containedwithin an enclosure body which may again be of tubular shape. Thetubular portion F2 is comprised by a porous hydrophilic material whichis Water receptive and through which water vapor may be readily pass.

Suitable materials are hydrophilic fine porous ceramics. Particularlysuitable are materials which have a small to negligible gas permeabilityand which transfer water by condensation in the pores preferably lessthan about Angstrom in diameter. One such material is known as porousVycor, a registered trade name for the precursor material to Vycor(registered trade name by Corning Glass Works who manufactures and sellssuch materials) which is used as a high silica laboratory glasswarematerial. This material is based on the property of certain borosilicateglasses to separate into two intertwining phases on heat treatment, oneof them being rich in boric acid and the other in silica. The boric acidphase then can be leached out and a fine porous high silica (over 90%)glass with pores about 35% pore volume) of around 20 to 40 Angstrom isformed. This material is extremely hydrophilic and has a low gaspermeability. However, water vapor condenses in the capillaries and israpidly transferred through the pores. Another material approaching theabove material is made by forming a network of silica gel in a plasticmatrix. While considerably more gas permeable, it becomes rapidly gasimpermeable after water is adsorbed. Coarser porous hydrophilic ceramicmaterials can be also used, but are less effective in rapidly absorbingwater.

Located about the hydrophilic tubular body F2 is a thin membrane M1which extends around opposite ends of the tubular member so as tocompletely cover this member. The membrane may be of a hydrophobicmaterial such as Teflon as earlier noted.

In this arrangement of catalytic components, a mechanism of hydrophobicgas inlets and water vapor outlets is also provided by the parts noted.Thus the porosity of the membrane M2, at opposite ends of the tubularenclosure, allows hydrogen and oxygen gases to enter into contact withthe catalyst pellets P7. Substantial portions of water vapor, formed atthe catalyst surfaces, will diffuse toward the hydrophilic surfaces ofthe hydrophilic component F2, and the water receptive nature of thissubstance provides for rapid absorption of the water vapor which isthereafter moved outwardly through the membrane M2 to condense outsideof the enclosure body.

In FIGS. 15-17, inclusive, there is illustrated a tubular structuresomewhat similar to that shown in FIGS. 12-14, with the difference thata tubular body F3, enclosing catalyst pellets P8, is made from Vycor orsimilar hydrophilic material and not protected by a hydrophobicmembrane. Ends of the tubular structure F3 are closed by caps C5 and C6.Such a device can be used where electrolyte spray is at a minimum and/orgood bafiles can protect the device sufliciently. Otherwise theoperation is the same as that of the device described in FIGS. 12-14.

FIGS. 18-20 inclusive, illustrate one of the simplest ways ofconstructing a device according to our invention, which, however, isperfectly operative when acid spray or other electrolyte mist problemsare minimal. There is again shown a bed of pellets 9 within a tubularbody of hydrophilic material such as porous Vycor F5. The ends of thetube are closed off with caps C11, C12 which are made from a hydrophobicmaterial such as a fiuorinated hydrocarbon polymer, which has narrow gasinlets C13, C14 which, to minimize any intrusion of liquids, havepreferably a small diameter such as 5 mm. or less and a length to heightratio of more than two. Of course, if larger gas access is desired, moreopenings of this kind can be arranged in either or both of the caps C11,C12. There may also be employed a spray baffle element R supported insome convenient manner at the under side of the device F5 as indicateddiagramatically.

From the disclosed operating results noted above in connection with thedescription of battery 202 (FIGS. 1-8 inclusive), it will be apparentthat the selective gas transferral system of the invention has beendemonstrated as an elfective means of overcoming the problems inpreventing accumulation of water on catalytic surfaces and returningwater of recombination to the electrolyte.

LAS further illustration of successful operation of the method of theinvention, there are noted below examples of a number of other simulatedbattery operations utilizing modifications of catalytic devicesgenerally corresponding to those illustrated in FIGS. 9 to 20. Thesetest procedures were carried out in specially devised testing equipmentconstructed to provide a simulated battery. This equipment consists in atransparent plastic casing capable of being hermetically sealed andcontaining a volume of sulfuric acid and also having two platinumelectrodes used to generate stoichiometric hydrogen and oxygen.

Catalyst devices to be tested were lowered in the casing immediatelyabove the level of the sulfuric acid and the casing was thereaftersealed. Electrolysis was then started and the current held at 1 amp forone-half hour and then at 50 milliamps for another one half hour.Electrolysis was then stopped and the catalyst was removed and inspectedfor water accumulation and acid contamination.

EXAMPLE A In order to establish a basis of comparison of the accumulation of water in a catalyst environment, a catalytic device wasfirst tested without the selective gas transfer system of the inventionbut being the same in all other respects. For this purpose, a catalystenclosure body having a nonporous hydrophilic portion as a substantialportion of the body was provided. The device had two end closures madefrom a fluorinated hydrocarbon polymer, of which one had an opening foradmitting gas. In this enclosure body were located a bed of catalystpellets of the type commonly used, such as .5% palladium by weightimpregnated about sq. m./g. pellets previously described. At the end ofa period of fifty-four minutes, elec-- trolysis was stopped andexamination of the catalytic device showed appreciable amounts ofcondensed water on the glass tube, occurring in amounts which would leadto catalyst failure after a short operating period.

EXAMPL'E B EXAMPLE C The procedure of Example B was again repeated withthe same equipment except that the Vycor tube was sprayed with sulfuricacid. Condensed water appeared on the inside of the Vycor tube afterapproximately 60 minutes, i.e., at the end of the first cycle, clearlyindicating that the Vycor is not completely resistant to electrolytespray.

EXAMPLE D The procedure of Example B was again carried out using thesame Vycor tube and other equipment but first applying to the Vycor tubea protective wrapping of a hydrophobic tape such as Teflon. The tape hada gas permeability as earlier disclosed and the device was sprayed withsulfuric acid in the manner carried out in Example C. After threecycles,no water of condensation was perceived on the interior of the Vycortube, indicating that unlike the device of Example C, the acidelectrolyte had been completely excluded.

EXAMPL'E E The'devices of Examples A, B, C, and D were found to beunable to fully consume the one-ampere gassing rate specified, and thusshowed a continuing pressure rise during operation because of the gasflow restriction caused by the small hole in the Teflon cap. A similardevice to that used in Example A, but with Teflon tape wrapped along itslength and covering both ends was constructed. This also showed no waterof condensation after several cycles and was, in addition, able toconsume gas from the one-ampere gassing rate at an equilibrium pressureof 1.3 atngospheres absolute (0.3 atmospheres of stoichiometn'c gas 1 7EXAMPLE F In another test operation, a device was made using hydrophobicmembranes for substantially the entire body. The device Was of the samedimensions as that of Example A and was made with a body of nylon meshwith the mesh being wrapped completely in Teflon tape. This device alsoshowed no water of condensation on the interior surfaces after a numberof cycles, and was easily able to consume a one-ampere gassing rate.

In addition to such simulated battery examples, extensive tests werecarried out in sealed batteries of the type described above, that isbatteries which were essentially sealed modifications of a minersbattery and having recombination devices incorporated therein. Typicalresults are illustrated in the following examples.

EXAMPLE G In this example a recombination device was constructed from apiece of porous Vycor tubing, 2.5 cm. long and 1.8 cm. outside diameter.This tubing was filled with grams of catalyst pellets of the compositetype and totally enclosed in a hydrophobic membrane by wrapping Teflontape over the ends and along the body of the device. This device wasthen placed into a modified mine lamp battery as noted above and thebattery was sealed and placed on a charge/ discharge cycle to simulatemine lamp battery operation which consisted of consecutive discharges atabout 1 amp for 1-0 hours followed by a full recharge over 14 hours. Thepressure and gas composition were continued, only monitored during eachcycle. Recombination of the gas inside the battery was indicated by therelatively low total pressure and the absence of all but a trace ofoxygen. This behavior was observed for several cycles and then thebattery was left on this continuous cycling regime for a period of sixmonths. At the end of this time, observations were being made on thetotal pressure and the gas composition inside the battery. The resultswere essentially the same as observed at the beginning of the periodwith oxygen only present in trace quantitles at the end of the chargecycle showing that the recombination device continued to be fullyeffective in recombining the hydrogen and oxygen produced primarilyduring the charge cycle.

EXAMPLE H In this example a recombination device was made from a pieceof a non-porous Teflon tube 1 inch long and 0.75 inches outsidediameter. Six grams of catalyst pellets of the type used in Example Gwere placed in this tube and the two ends covered with a porous Teflonmembrane as used for filter purposes and previously described and sealedwith epoxy cement. This device was placed into a similarly modified minelamp battery on a charge/discharge cycle as in Example G. Pressure andthe gas composition measurements made as before showed that therecombination device was recombining all of the hydrogen and oxygenproduced during the charge cycles. This battery was placed on continuouscharge/ discharge cycles to simulate mine lamp battery operation for aperiod of five months. At the end of that time further measurements ofthe pressure and gas composition showed that the unit continued to befully Capable of recombining all the hydrogen and oxygen gas producedduring each charge cycle.

From the foregoing disclosure of our invention it will be apparent thatwe have provided an improved technique and improved means forrecombining gases and releasing water of recombination in theelectrolyte body from which it evolved while at all times maintainingthe catalyst means substantially free from electrolyte mist andaccumulation of Water.

We claim:

1. A hydrogen-oxygen recombining device for use in a secondary batteryhaving an electrolyte therein comprising a catalytic mass and anenclosure body having the catalytic mass totally enclosed therewithin,said catalytic mass including a refractory substrate and a predeterminedquantity of catalytic material distributed on said substrate, saidenclosure body consisting solely of plastic hydrophobic material andhaving a portion which is gas permeable, said hydrophobic materialincluding said permeable portion preventing liquid and mist from thebattery electrolyte from entering said body and contaminating saidcatalytic mass, said permeable portion permitting the hydrogen andoxygen to enter said body and contact said catalytic mass and saidpermeable portion permitting water vapor formed by recombining theoxygen and hydrogen to diffuse from said body, said catalytic masshaving a catalytic metal content equivalent to a palladium content ofnot more than .1% by weight of the substrate, said catalytic mass, wheninducing an exothermic reaction to recombine the hydrogen and oxygen,being characterized by a limited temperature rise within limits belowthat References Cited UNITED STATES PATENTS 3,102,059 8/1963 Harmer136-181 3,258,360 6/1966 Kordesch 1366 GC JOSEPH SCOVRONEK, PrimaryExaminer US. 01. X.R.

